assignment1.java

計平均數的java program, 含string tokenizer和error detection, 分便初學者學習

/*import java.util.StringTokenizer;
import java.util.Scanner;*/
/*import java.lang.StringBuffer;
import java.lang.String;*/
import java.util.*;
//import java.lang.*;
public class assignment1
{
	public static void main(String[] args)
	{
	    String str, recalc;
	    Boolean run=true,input=true;
        int total, number_of_input=0;
		 do
		 {
			run=true;
			System.out.println("Please enter the integers to average, separated by spaces (e.g., 1 2 3 4):");
			Scanner scanner = new Scanner(System.in);
			str = scanner.nextLine();
			char [] checking=str.toCharArray();
			for (int x=0; x<str.length();x++)
			{
				if ((Character.isDigit(checking[x])==false) && (checking[x]!=' '))
					run=false;
			}
			if  (str.length()<=0)
				run=false;
			if (run==false)
				System.out.println("Invalid input.");
			else
			{
				total=0;
				StringTokenizer tokenizer = new StringTokenizer(str);
				number_of_input = tokenizer.countTokens();
				while(tokenizer.hasMoreTokens()){
					total+=Integer.parseInt(tokenizer.nextToken());
				}
				double average = (double) total / number_of_input;
				System.out.printf("The average of the %d numbers is %.2f.\n",
						number_of_input, average);
			}
	        run=true;
	        do
	        {
	        	input=true;
	        	System.out.print("Calculate another average? (Yes/No):");
	        	recalc=scanner.nextLine();
	        	if (recalc.equalsIgnoreCase("Yes")|| recalc.equalsIgnoreCase("No"))
	        	{
	        		input=false;
	        		if (recalc.equalsIgnoreCase("No"))
	        			run=false;
	        	}
	        }
	        while (input);
		}
		while (run);
		System.out.println("Bye.");
	}
}